By the method of anterograde degeneration, distribution of projections of functionally definite AI and AIV zones of the cat auditory cortex have been studied in the posterior calculi of the tectum opticum. It has been demonstrated electron microscopically that an essentially part of the degenerating boutons are found in the middle and caudal thirds of the colliculi, and the remaining ones terminate on the dendrites with large- and middle-size diameters and on the spines. A supposition is made that there exist two systems of the corticofugal auditory fibres. Peculiarities of the degenerative rates, specific for short- and long-axonal systems of the fibres and possible mechanisms for the influence of the auditory cortex on the neurons of the posterior colliculi of the tectum opticum are discussed.